This invention relates to cathode-ray tubes having cathodoluminescent line screens and slit apertured masks therein, and particularly to a screen structure of improved visual acceptance.
Recent cathode-ray tubes developed and marketed for use in color television receivers have spherically-contoured rectangular faceplates with line screens of cathodoluminescent materials thereon and somewhat spherically contoured slit-apertured shadow masks adjacent to the screens. The mask slits are aligned in parallel vertical columns. Each column contains a plurality of slits which are vertically separated by web portions of the mask. The web portions in adjacent columns are vertically staggered relative to each other. Because of this staggering and because the slit apertures generally are held constant in length, designated top and bottom border lines primarily cut through apertures in each column but also, often cut through web portions. The net effect on the screen of having some columns abutting the desired borderline with webs while the remaining columns abut the border line with apertures is the formation of steps in some portions of the top and bottom borders of the screen. Such steps in the screen can be seen by an observer sitting close to the screen and therefore are aesthetically undesirable.